Straight stitch control mechanisms for zigzag sewing machines



Jan. 20, 1970 D, P. BUAN ET AL STRAIGHT STITCH CONTROL MECHANISMS FORZIGZAG SEWING MACHINES Filed NOV. 20, 1967 2 Sheets-Sheet 1 BY Augus?WiTNESS:

m mne m N w w m n T m M Jan. 20, 1970 D. P. BUAN ET AL 3,490,400

STRAIGHT STITCH CONTROL MECHANISMS FOR ZIGZAG SEWING MACHINES Filed Nov.20, 196 2 Sheets-Sheet 2 IN VENTORS' Duniio P Buan and ugusi Mqnieim.IGML NTTQRNEY United States Patent 3,490,400 STRAIGHT STITCH CONTROLMECHANISMS FOR ZIGZAG SEWING MACHINES Danilo P. Buan, Old Bridge, andAugust Monteiro, Kearny,

N.J., assignors to The Singer Company, New York,

N.Y., a corporation of New Jerse Filed Nov. 20, 1967, Ser. No. 684,430Int. Cl. D05b 3/02 US. Cl. 112158 6 Claims ABSTRACT OF THE DISCLOSURE Alever operated by means for changing the stitch width of a zigzag sewingmachine serves to move connecting means to a needle bar gate out ofcontact with cam follower means when the means for changing the stitchwidth is set for zero stitch width.

BACKGROUND OF THE INVENTION The invention relates to control means forreadying a zigzag sewing machine to sew straight stitches.

DESCRIPTION OF THE PRIOR ART Sewing machines which can sew a widevariety of different stitch patterns have been increasingly demanded byconsumers. However, straight sitch sewing constitutes perhaps the mostfrequent operation performed by a sewing machine. In one type of sewingmachine which can sew a wide variety of stitch patterns, a wobble plateis pivotally mounted on the end of a rod connected to a needle bar gate,and the connecting rod is spring biased against a cam follower and afulcrum projection. The cam follower tracks a cam which is mounted on acam shaft. Also mounted on the cam shaft is a bracket having a universaljoint connection to the wobble plate. By shifting the angular positionof the bracket on the cam shaft, the wobble plate can be movedrelatively to the fulcrum projection and the cam follower in order tochange the width of lateral movement of the needle in zigzag sewing. Theextent of such lateral motion is termed stitch width. When the Wobbleplate is positioned so that the fulcrum projection bears directlyopposite the pivoted mount for the wobble plate, the zero stitch widthwill occur. It can be appreciated that for uniform straight stitchsewing to be formed relying upon such zero stitch width setting, a mostprecise orientation of the wobble plate is necessary. However,economically feasible machine tolerances, the tendency of parts to getout of adjustment, and normal wear of parts have militated againstobtainment of this degree of precision.

SUMMARY OF THE INVENTION It is therefore a primary object of theinvention to provide an improved straight stitch control mechanism for azigzag sewing machine of the type having abutment means on connectingmeans to a needle bar gate spring biased against a cam follower means inwhich it is possible to obtain consistent uniform straight stitches.

Another object of the invention is to provide an improved straightstitch control mechanism in accordance with the foregoing object inwhich the abutment means on the connecting means to the needle bar gateis held out of contact with the cam follower means when the stitch widthcontrol mechanism is set for zero stitch width.

Another object of the invention is to provide an improved straightstitch control mechanism in accordance with the foregoing object inwhich the abutment means on the connecting means to the needle bar gateis moved out of contact with the cam follower means in response to thesame operator influence by which the stitch width control mechanism isset for zero stitch width.

3,490,400 Patented Jan. 20, 1970 Other objects and a fullerunderstanding of the invention can be had by referring to thedescription and claims taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a sewingmachine with the top cover removed to show the improved straight stitchcontrol mechanism of this invention;

FIG. 2 is a front elevational view of the upper portion of the controlpanel on the front of the bracket arm and standard of FIG. 1;

FIG. 3 is a cross sectional view taken along the line 3--3 in FIG. 1;and

FIG. 4 is an exploded perspective view of the improved straight stitchwidth control mechanism of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the drawings,in FIG. 1 the invention is shown embodied in a sewing machine having aframe 11 of which the top of a standard 12, a bracket arm 13 extendinglaterally from the top of the standard, and a sewing head 14 at the freeend of the bracket arm are shown. The top of the frame is covered by atop cover 15, as shown in FIG. 3. In FIG. 1, the top cover is removed toshow the inside of the lbracket arm. A control panel 16 is connected tothe front of the bracket arm and standard. Mounted between the bracketarm and the control panel on two bosses 17 on the bracket arm is a plate18 which is held by screws 19 threaded one into each of the bosses. Twoslotted apertures, 20 and 21, are formed in the plate in line with twoslotted apertures 22 and 23, in the bracket arm and also in line withtwo slotted apertures 24 and 25, formed in the control panel. As shownin FIG. 2, indicia L, C and R are formed above the uppermost slottedaperture 24 in the control panel, and indicia 1 to 5 are formed abovethe lower-most slotted aperture 25 in the control panel. A notch 26 isformed in the upper edge of the lowermost slotted aperture 25 in thecontrol panel beneath the indicia 1. The indicia 1 represents zerostitch width, while the indicia 5 represents maximum stitch width. Theindicia L, C, and R above the uppermost slotted aperture represent left,center, and right needle positions, respectively. Mounted in the sewinghead is a needle lbar gate 27, which is pivotally connected at anintermediate portion to the sewing head 14 by a hinge pin 28. A needlebar 29 is slidably mounted in the front end of the needle bar gate.Endwise reciprocating motion is imparted to the needle bar by aconventional crank mechanism indicated generally at 30. The crankmechanism is fast on an arm shaft 31 which extends longitudinallythrough the bracket arm 13 and is journaled in two partitions 32 and 33,one in the head end of the bracket arm and the other in the top of thestandard. A hand wheel 34 is mounted on the standard end of the armshaft. Pivotally connected to the rearmost end of the needle bar gate bya pivot screw 35 is a connecting rod 36, the free end of which extendsinto the bracket arm. An abutment means is carried by a connecting rodagainst which control impulses are directed to influence the lateralposition of the needle bar. Preferably the abutment means takes the formof a wobble plate 37, which is pivotally connected to the free end ofthe connecting rod by a vertical hinge pin 38. Pivotally mounted in thebottom of the bracket arm in the vicinity of the wobble plate 'bya'pivot screw 39 is a bell crank 40 having two arms 41 and 42, of whichone arm 41 is formed in the shape of a hook. A tension coil spring 43 isstretched between the hooked arm 41 of the bell crank and a stud 44 onthe rearmost end of the needle bar gate biasing the other arm 42 of thebell crank against the 3 wobble plate 37 thus to bias the wobble platetowards the standard end of the sewing machine.

Journaled in a boss in the bracket arm is a cam shaft 46. A bracket 47pivotally mounted on the cam shaft has upper ring 48, and a circularhole 49 to receive a spherical bearing 50 connected to the free end ofthe connecting rod 36 to the needle bar gate. The foregoing arrangementforms a universal joint between the bracket 47 and the connecting rod. Asimilar arrangement is dis closed in the United States patent of R. E.Johnson, No. 2,862,468; granted Dec. 2, 1958. Rotation is imparted tothe cam shaft by a worm 51 on the arm shaft and a meshing worm wheel 52on the cam shaft. A cam 53 having a. peripheral cam surface 54 isexchangeably mounted on a flange 55 on the cam shaft and yieldably heldon the flange by a spring clip 56. The cam is fixed to rotate with thecam shaft by a pin 57 on the flange extending into a hole 58 in the cam.

Pivotally mounted on a boss 59 in the bracket arm by a pivot screw 60 isa needle position lever 61. The needle position lever has a fulcrumprojection 62 which bears against the wobble plate 37. A handle 63 isconnected to the free end of the needle position lever by two screws 64and 65. The handle extends through the uppermost slotted apertures 22,20, 24 in the front of the bracket arm, the plate, and the controlpanel, respectively. A knob 66 is formed on the free end of the handle.

Mounted in another boss 67 in the bracket arm by a set-screw 68 is apost 69. The post has an upper pilot portion 70 forming a shoulder 71 asshown in FIG. 4, a U-shaped cam follower means 72 having lower and upperarms 73 and 74, respectively, is pivotally mounted on the pilot portionof the post with the pilot portion extending through aligned bores 75and 76 formed in the lower and upper arms, and the lower arm resting onthe shoulder 71 of the post. An upwardly extending cam follower 77 isformed on the upper arm 74 of the cam follower means to contact theperipheral cam surface 53 of the exchangeable cam.

A11 upwardly extending handle 78 is also formed on the upper arm of thecam follower means. Pivotally mounted on the pilot portion 70 of thepost above the lower arm of the cam follower means is a throw-out lever79, having a clearance bore 80 for the pilot portion of the post. Thethrow-out lever has a cam surface 81, and is biased by a torsion spring82, mounted on the pilot portion of the post above the lever. Thetorsion spring has two limbs 83 and 84 of which one arm 83 bears againstthe lower arm of the cam follower means 72 and the other arm 84 bearsagainst the lever to bias the lever in a counterclockwise direction.Mounted on the upper arm of the cam follower means is a contactingmember 85 for contacting the wobble gate 37. The contacting member has aclearance bore 86 for the pilot portion of the post and-is connected tothe upper arm 74 of the cam follower means 72 by two screws 87 and 88.One of the two screws extends through a clearance hole 89 in thecontacting member into a tapped hole 90 in the upper arm of the camfollower means. The other screw 88 is a shoulder screw on which aneccentric sleeve 91 with a hexagonal upper portion 92 is pivotallymounted. The eccentric sleeve 91 extends into a slot 93 in thecontacting member and the screw 85 threads into a tapped hole 94 in theupper arm of the cam follower means. The eccentric 91 member provides aslight lateral adjustment feature for the contacting member so that thezigzag motion of the needle bar may be laterally adjusted. The camfollower means is held on the pilot portion of the post by a collar 95with a setscrew 96.

Connected to the ring 48 of the bracket 47 which is connected to the endof the connecting rod 36 to the needle bar gate by the spherical bearing40 on the connecting rod, is a stitch width control lever 97. The stitchwidth control lever is connected to the ring of the bracket by twoscrews 98 and 99. A handle 100 is connected to the free end of thestitch width control lever by a screw 101 and a stud 102 which preventspivotal movement of the handle about the last mentioned screw 101. Thehandle extends through the lowermost slotted apertures 23, 21, 25, inthe front of the bracket arm, the plate, and the control panel,respectively. A knob 103 is formed on the free end of the handle.Mounted on the two screws 98 and 99 which connect the stitch Widthcontrol lever to the ring of the bracket is a camming member 104 forhearing against the cam surface 81 on the lever 79 on the post. Thecamming member has two clearance slots 105 and 106 for the screws 98 and99 and an upwardly projecting handle to provide a lateral adjustmentfeature.

In operation, when it is desired to sew straight stitches, the handle100 of the stitch width control lever 97 is moved into the notch 26 inthe upper edge of the lowermost slotted aperture in the control panelbeneath the indicia 1. The foregoing movement causes the camming member104 on the stitch width control lever to bear against the cam surface 81on the throw-out lever 79 which is properly positioned by the torsionspring 82. The foregoing movement causes the throwout lever 79 to pivotin a counterclockwise direction on the pilot portion 70 of the post 69to force the wobble plate 37 out of contact with the contacting member85 on the cam fol lower means 72 in opposition to the tension coilspring 36. Thus, the sewing machine is free to sew perfectly straightstitches uninfluenced by any slight movement of the wobble plat 37 whichmight be caused by wide tolerances, parts out of adjustment, or wornparts. The foregoing is accomplished without adding any additionaloperation on the part of an operator, and irregardless of whether theneedle position control lever is in left, center, or right position.

Although the invention has been described in its preferred form with acertain degree of particularity, it is understood that the presentdisclosure of the preferred form has been made by way of example andthat numerous changes in the details of construction and the combinationand arrangement of parts can be resorted to without departing from thespirit and the scope of the invention.

Having thus set forth the nature of this invention, what is claimedherein is:

1. In a zigzag sewing machine having a frame, a needle bar gate mountedin the frame, a needle bar mounted on the needle bar gate, a cam shaftmounted in the frame, means for imparting rotation to the cam shaft, acam having a cam surface mounted on the cam shaft for rotation with thecam shaft to impart lateral oscillation to the needle bar gate, camfollower means mounted in the frame, a cam follower on the cam followermeans for contact with the cam surface of the cam, a contacting means onthe cam follower means for movement with the cam follower, a connectingmeans having one end connected to the needle bar gate for transmittinglateral oscillation to the needle bar gate, abutment means at the otherend of the connecting means for engaging the contacting means on the camfollower means, means for biasing the abutment means on said connectingmeans against the contacting means on said cam follower means, andoperator influenced means for changing the stitch width from zero to apredetermined maximum, an improved straight stitch control mechanismincluding a throw-out lever operated by the means for changing thestitch width to move the abutment means on the connecting means out ofengagement with said contacting means on said cam follower means whensaid means for changing the stitch width is shifted into a positiondictating a zero stitch width.

2. The improved straight stitch control mechanism of claim 1 in whichthe throw-out lever has a cam surface and the means for changing thestitch width includes a camming means which bears against the camsurface of the lever when the means for changing the stitch Width is setfor zero stitch width to cause the throw-out lever to move the abutmentmeans on the connecting means out of engagement with the contactingmeans on said cam follower.

3. The improved straight stitch control mechanism of claim 2 in whichthe means for changing the stitch width includes a stitch width controllever and said camming means is on the stitch width control lever.

4. The improved stitch width control mechanism of claim 3 which includesmeans for adjusting the position of the said camming means on saidstitch width control I lever.

5. The improved straight stitch control mechanism of claim 1, in whichthe cam follower comprises a lever, and in which a single pivotalmounting means in the sewing machine pivotally supports both the camfollower lever andthe throw-out lever.

6. The improved straight stitch control mechanism of claim 5 whichincludes a torsion spring having two limbs mounted on the means forpivotally mounting the lever and the cam 'follower lever, with one ofthe torsion spring limbs bearing against the cam follower means and theother torsion spring limb bearing against the throwout lever to bias thecam surface of the throw-out lever into a position for receiving thecamming means when the means for changing the stitch width is set forzero stitch width.

References Cited UNITED STATES PATENTS 3,081,724 3/1963 .1 Bono 1l2158RICHARD J. SCANLON, JR., Primary Examiner

